I'll try some setups when I come back from Christmas vacations, but I was never ever able to supply any size of boiler with any tree farm, either we run out of wood to transform to charcoal, or I run out of power for the farm itself before even reaching the critical 100°C on the boiler... Maybe I have bad luck because most of my setup is on a server and even if the area is chunkloaded, it doesn't work properly or something like that...
Oi, the problems are multifold-
#1, HEATING UP THE BOILER-
You cannot just put an auto tree farm/charcoal /boiler setup in place and expect it to work. You need a BUNCH of stacks of charcoal when you are starting the boiler in the first place, and depending on it's size, it can take a LONG time, several hours, to get up to proper heat. the farm works just fine for MAINTAINING a boiler, but initial startup? not a snowball's chance in a furnace. Try creating an entire chest full of charcoal, running that to your boiler, then having your tree farm/charcoal setup run to that chest, instead of running it directly in.
#2, CHUNK LOADING-
If you cannot have a consistent chunk load, running a boiler is a total waste of time except for the very smallest size. Big boilers have to keep running ALL THE TIME in order to have any efficiency.... if you lose loaded status on a boiler for any reason, it's simply more efficient to use alternate, faster sources of energy, such creosote and charcoal from ranks of coke ovens feeding to generators, or a thermal expansion charcoal(steam dynamo/cobblegen to lava in melter/magmatic dynamo) to high energy power source.... bonus points if you are playing tech world with ender IO capacitors that can shut off the network to avoid wasting fuel if things slow down.
Boilers are truly outstanding alternatives to reactors if you need long term power, with guaranteed chunkloading, but any unstable situation and you are going to rip through your fuel in constant restarts and probably beat your head against a wall trying to keep the darned thing from wasting all your time and patience.
I don't blame you for trying, but maybe you need to practice creating MFR treefarm/boiler setups in solo creative mode before you can be truly comfortable tackling the monster on a server. Handled correctly (try using extra utilities pipes with filters?) even an iron-upgraded MFR tree farm can keep all but the largest boilers maintained comfortably... with the added bonus of a disgusting huge surplus of apples and saplings (You can even pump the saplings into the biofuel generator for an added power tweak to your network! a little stable power goes a LONG way.)
Frankly, I am rather surprised that CJ never added a 'preheat' ability to boilers, via netherrack fires under the fireboxes, heaters from other mods, or lava.
is temperature a forge variable? I would LOVE for that functionality to be added... imagine if factorization or rotarycraft heaters could help preheat fireboxes?